feat: add the notification mechanism implementation (#4527)

#### What type of PR is this?
/kind feature
/milestone 2.10.x
/area core

#### What this PR does / why we need it:
新增消息和通知机制的实现

how to test it?
1. 执行以下命令配置发件服务
```shell
curl -u admin:admin -X POST 'http://localhost:8090/apis/api.console.halo.run/v1alpha1/notifiers/default-email-notifier/senderConfig' \
--header 'Content-Type: application/json' \
--data-raw '{
    "displayName": "Halo Team",
    "username": "{发件使用的邮箱}",
    "password": "{发件邮箱密码}",
    "host": "smtp.exmail.qq.com",
    "port": "587"
}'
```
2. 评论文章或页面可以收到通知
3. 文章/页面作者是评论者不发送新评论通知，回复者是评论作者不发送回复通知

#### Which issue(s) this PR fixes:
Fixes #4045

#### Does this PR introduce a user-facing change?
```release-note
新增消息和通知机制的实现
```

api/src/main/java/run/halo/app/content/comment/CommentSubject.java

@@ -11,9 +11,16 @@
  * @author guqing
  * @since 2.0.0
  */
-public interface CommentSubject<T extends Extension>  extends ExtensionPoint {
+public interface CommentSubject<T extends Extension> extends ExtensionPoint {
 
     Mono<T> get(String name);
 
+    default Mono<SubjectDisplay> getSubjectDisplay(String name) {
+        return Mono.empty();
+    }
+
     boolean supports(Ref ref);
+
+    record SubjectDisplay(String title, String url, String kindName) {
+    }
 }

api/src/main/java/run/halo/app/core/extension/notification/Notification.java

@@ -0,0 +1,58 @@
+package run.halo.app.core.extension.notification;
+
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import java.time.Instant;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import run.halo.app.extension.AbstractExtension;
+import run.halo.app.extension.GVK;
+
+/**
+ * <p>{@link Notification} is a custom extension that used to store notification information for
+ * inner use, it's on-site notification.</p>
+ *
+ * <p>Supports the following operations:</p>
+ * <ul>
+ *    <li>Marked as read: {@link NotificationSpec#setUnread(boolean)}</li>
+ *    <li>Get the last read time: {@link NotificationSpec#getLastReadAt()}</li>
+ *    <li>Filter by recipient: {@link NotificationSpec#getRecipient()}</li>
+ * </ul>
+ *
+ * @author guqing
+ * @see Reason
+ * @see ReasonType
+ * @since 2.10.0
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+@GVK(group = "notification.halo.run", version = "v1alpha1", kind = "Notification", plural =
+    "notifications", singular = "notification")
+public class Notification extends AbstractExtension {
+
+    @Schema
+    private NotificationSpec spec;
+
+    @Data
+    public static class NotificationSpec {
+        @Schema(requiredMode = REQUIRED, minLength = 1, description = "The name of user")
+        private String recipient;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1, description = "The name of reason")
+        private String reason;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String title;
+
+        @Schema(requiredMode = REQUIRED)
+        private String rawContent;
+
+        @Schema(requiredMode = REQUIRED)
+        private String htmlContent;
+
+        private boolean unread;
+
+        private Instant lastReadAt;
+    }
+}

api/src/main/java/run/halo/app/core/extension/notification/NotificationTemplate.java

@@ -0,0 +1,59 @@
+package run.halo.app.core.extension.notification;
+
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import run.halo.app.extension.AbstractExtension;
+import run.halo.app.extension.GVK;
+
+/**
+ * <p>{@link NotificationTemplate} is a custom extension that defines a notification template.</p>
+ * <p>It describes the notification template's name, description, and the template content.</p>
+ * <p>{@link Spec#getReasonSelector()} is used to select the template by reasonType and language,
+ * if multiple templates are matched, the best match will be selected. This is useful when you
+ * want to override the default template.</p>
+ *
+ * @author guqing
+ * @since 2.10.0
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+@GVK(group = "notification.halo.run", version = "v1alpha1", kind = "NotificationTemplate",
+    plural = "notificationtemplates", singular = "notificationtemplate")
+public class NotificationTemplate extends AbstractExtension {
+
+    @Schema
+    private Spec spec;
+
+    @Data
+    @Schema(name = "NotificationTemplateSpec")
+    public static class Spec {
+        @Schema
+        private ReasonSelector reasonSelector;
+
+        @Schema
+        private Template template;
+    }
+
+    @Data
+    @Schema(name = "TemplateContent")
+    public static class Template {
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String title;
+
+        private String htmlBody;
+
+        private String rawBody;
+    }
+
+    @Data
+    public static class ReasonSelector {
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String reasonType;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1, defaultValue = "default")
+        private String language;
+    }
+}

api/src/main/java/run/halo/app/core/extension/notification/NotifierDescriptor.java

@@ -0,0 +1,54 @@
+package run.halo.app.core.extension.notification;
+
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import run.halo.app.extension.AbstractExtension;
+import run.halo.app.extension.GVK;
+
+/**
+ * <p>{@link NotifierDescriptor} is a custom extension that defines a notifier.</p>
+ * <p>It describes the notifier's name, description, and the extension name of the notifier to
+ * let the user know what the notifier is and what it can do in the UI and also let the
+ * {@code NotificationCenter} know how to load the notifier and prepare the notifier's settings.</p>
+ *
+ * @author guqing
+ * @since 2.10.0
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+@GVK(group = "notification.halo.run", version = "v1alpha1", kind = "NotifierDescriptor",
+    plural = "notifierDescriptors", singular = "notifierDescriptor")
+public class NotifierDescriptor extends AbstractExtension {
+
+    @Schema
+    private Spec spec;
+
+    @Data
+    @Schema(name = "NotifierDescriptorSpec")
+    public static class Spec {
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String displayName;
+
+        private String description;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String notifierExtName;
+
+        private SettingRef senderSettingRef;
+
+        private SettingRef receiverSettingRef;
+    }
+
+    @Data
+    @Schema(name = "NotifierSettingRef")
+    public static class SettingRef {
+        @Schema(requiredMode = REQUIRED)
+        private String name;
+
+        @Schema(requiredMode = REQUIRED)
+        private String group;
+    }
+}

api/src/main/java/run/halo/app/core/extension/notification/Reason.java

@@ -0,0 +1,70 @@
+package run.halo.app.core.extension.notification;
+
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.NOT_REQUIRED;
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.NoArgsConstructor;
+import run.halo.app.extension.AbstractExtension;
+import run.halo.app.extension.GVK;
+import run.halo.app.notification.ReasonAttributes;
+
+/**
+ * <p>{@link Reason} is a custom extension that defines a reason for a notification, It represents
+ * an instance of a {@link ReasonType}.</p>
+ * <p>It can be understood as an event that triggers a notification.</p>
+ *
+ * @author guqing
+ * @since 2.10.0
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+@GVK(group = "notification.halo.run", version = "v1alpha1", kind = "Reason", plural =
+    "reasons", singular = "reason")
+public class Reason extends AbstractExtension {
+
+    @Schema
+    private Spec spec;
+
+    @Data
+    @Schema(name = "ReasonSpec")
+    public static class Spec {
+        @Schema(requiredMode = REQUIRED)
+        private String reasonType;
+
+        @Schema(requiredMode = REQUIRED)
+        private Subject subject;
+
+        @Schema(requiredMode = REQUIRED)
+        private String author;
+
+        @Schema(implementation = ReasonAttributes.class, requiredMode = NOT_REQUIRED,
+            description = "Attributes used to transfer data")
+        private ReasonAttributes attributes;
+    }
+
+    @Data
+    @Builder
+    @NoArgsConstructor
+    @AllArgsConstructor
+    @Schema(name = "ReasonSubject")
+    public static class Subject {
+        @Schema(requiredMode = REQUIRED)
+        private String apiVersion;
+
+        @Schema(requiredMode = REQUIRED)
+        private String kind;
+
+        @Schema(requiredMode = REQUIRED)
+        private String name;
+
+        @Schema(requiredMode = REQUIRED)
+        private String title;
+
+        private String url;
+    }
+}

api/src/main/java/run/halo/app/core/extension/notification/ReasonType.java

@@ -0,0 +1,58 @@
+package run.halo.app.core.extension.notification;
+
+import static io.swagger.v3.oas.annotations.media.Schema.RequiredMode.REQUIRED;
+
+import io.swagger.v3.oas.annotations.media.Schema;
+import java.util.List;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import run.halo.app.extension.AbstractExtension;
+import run.halo.app.extension.GVK;
+
+/**
+ * <p>{@link ReasonType} is a custom extension that defines a type of reason.</p>
+ * <p>One {@link ReasonType} can have multiple {@link Reason}s to notify.</p>
+ *
+ * @author guqing
+ * @see NotificationTemplate
+ * @see Reason
+ * @since 2.10.0
+ */
+@Data
+@EqualsAndHashCode(callSuper = true)
+@GVK(group = "notification.halo.run", version = "v1alpha1", kind = "ReasonType",
+    plural = "reasontypes", singular = "reasontype")
+public class ReasonType extends AbstractExtension {
+    public static final String LOCALIZED_RESOURCE_NAME_ANNO =
+        "notification.halo.run/localized-resource-name";
+
+    @Schema
+    private Spec spec;
+
+    @Data
+    @Schema(name = "ReasonTypeSpec")
+    public static class Spec {
+
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String displayName;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String description;
+
+        private List<ReasonProperty> properties;
+    }
+
+    @Data
+    public static class ReasonProperty {
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String name;
+
+        @Schema(requiredMode = REQUIRED, minLength = 1)
+        private String type;
+
+        private String description;
+
+        @Schema(defaultValue = "false")
+        private boolean optional;
+    }
+}